Wound Prep Series: Soap

So, you’ve managed to painlessly anesthetize your patient’s laceration, with a combination of topical and injected anesthetic. The wound has been irrigated with your solution of choice under optimal pressure. Now it’s time to prepare the field for your repair. You reach in to your wound supply cabinet and stare at the bottle of povidone-iodide (Betadine), the chlorhexadine swabs, and wonder…which is better? Do I really need to bother with either of them?

Iodine-containing solutions for wound care have been a mainstay of antisepsis for over a century. But lately it seems they’ve gotten a bit of a bad rap. I feel like I hear more about their toxicity to tissues and theoretical impediment to wound healing than about their benefits in protecting against the baddies. In this respect I think the pendulum has swung a bit too far, and this post is meant to set the record straight.

In defense of iodine

Iodine was discovered in the 17th century and has been broadly used for the prevention of skin infections and treatment of wounds since that time. Iodine is bactericidal, and is also effective against yeasts, molds, fungi, viruses, and protozoans. However, pure iodine application can lead to tissue toxicity, and the staining of surrounding tissues. These deficiencies were overcome by the discovery and use of povidone-iodine, in which the iodine is carried in a complexed form (povidone, hydrogen iodide, and elemental iodine) where the concentration of free iodine is very low.

The more recent belief that iodine containing antiseptics can be detrimental to wound healing is actually based on now decades-old reports from surgical literature (Lineaweaver W, et al, Brånemark PI, et al, Rodeheaver G, et al). In practice, iodine doesn’t really seem to have this purported detriment to wound healing. It doesn’t really seem to have much effect at all.

A 2010 meta-analysis examined this in detail. Among 7 trials in a subgroup focused on the iodine-related effects on acute wounds, measures favoring iodine and against it seemed split nearly down the middle. No strong conclusion was drawn by the authors regarding its use, except to say that it’s undoubtedly the most well-studied topical antiseptic agent in existence, and at the very least, safe. That is to say, the reports of it causing death to tissue were greatly exaggerated.

A 2015 Cochrane database review came out slightly in favor of chlorhexadine over povidone-iodine for prevention of surgical site infection, but called for a larger, more definitive study to be performed before drawing any final conclusions. This was an echoed sentiment in a 2017 meta-analysis, which also noted that fewer skin cultures are positive with the use of chlorhexadine.

Also worth noting: many of the studies of iodine compared its safety and efficacy with that of novel, commercial products. Remember, betadine is cheap and not likely to have any industry backing in its corner. Further, many of the studies are over a decade old, pre-dating the CONSORT statement and current research methodology standards.

This now said, let me turn your attention to a few more recent and ED-focused studies that also considered the role of povodine-iodine in wound management. The authors of this 2016 study compared normal saline irrigation to irrigation with a dilute, 1% povidone-iodine solution for acute traumatic lacerations. The results: wound infection rates were not statistically significant between groups, holding steady at around 7% in each arm. I’ve seen the dilute povidine bit employed by some and I’ve never thought it was worth the effort myself–this study seems to support this.

Here’s another 2016 study more akin to what we do: the comparison was a single center RCT of betadine painted around the margins of a traumatic laceration prior to closure, compared with no betadine. The result: no difference in infection rates was noted, and infection rates again remained low in both groups. However, this study lacked a statement of power calculation and its unclear if the authors were at risk of a Type II error. They state as much in their conclusions: despite their results, they don’t recommend any change in routine ED traumatic wound management just yet.

Summary & Recommendations:

Despite some recent work in the field of best antisepsis prior to emergency department wound closure, there simply isn’t evidence to support a definitive best recommendation.

How I do it: I am not super-particular about it, but if both are available to me, I will reach for the chlorhexadine. It’s clear and leaves less of a clean-up, and it’s slightly favored by the evidence presented above.

If povidine-iodine is all there is, I still use it, painted around the wound edges but not within the wound. And if a little gets in there accidentally, I don’t panic.

That’s the final deposit in this 5 part series on best practice in wound preparation. Up next month, something a little more fun: my presentation on tissue adhesive glues to the audience at Nerdnite San Francisco!